Numerous devices have been advanced each having one unit attached to the towing vehicle and another unit carried by the hitch or towing tongue of the vehicle to be towed. Such devices are shown and described in the following U.S. patents:
Hamilton--U.S. Pat. No. 2,984,011 PA1 Anderson--U.S. Pat. No. 3,702,029 PA1 Voelkerding et al--U.S. Pat. No. 3,765,703 PA1 Lakamp--U.S. Pat. No. 3,867,898 PA1 Alexander et al--U.S. Pat. No. 3,866,328 PA1 White--U.S. Pat. No. 3,889,384 PA1 Lehtisaari--U.S. Pat. No. 3,918,746 PA1 Vankrevelen--U.S. Pat. No. 4,156,972 PA1 Campbell--U.S. Pat. No. 4,054,302 PA1 Bohnet--U.S. Pat. No. 3,015,162 PA1 Tague--U.S. Pat. No. 3,818,599
The art to which particular attention is directed
however neither prior art structure teaches the use of a pair of quickly applied magnetic bases and wands with signal flags and gromets for cooperating with a pair of plumb lines each having a plumb bob positionable directly over the towing ball on one hand and the trailer socket on the other hand which vertical alignment will control the position of the alignment signal flags on the respective wands so that when the towing vehicle backs toward the trailer vehicle, when the flags cross hookup can be effectuated, thereafter, the bases, wands and plumb lines may be removed to avoid theft either during transport or periods of non-use.